US3921003A

US3921003A - Apparatus for identifying coins

Info

Publication number: US3921003A
Application number: US511433A
Authority: US
Inventors: Walter John Greene
Original assignee: Mars Inc
Current assignee: Mars Inc
Priority date: 1973-10-03
Filing date: 1974-10-02
Publication date: 1975-11-18
Anticipated expiration: 1992-11-18
Also published as: GB1453283A

Abstract

An apparatus for identifying acceptable coins, including a coin track assembly having a circular coin track loop around which coins can roll, sensor means focused at the center of the circular coin track loop for generating a signal in response to the coin surface pattern as the coin rolls around the circular coin track loop and means for monitoring the signal output from the sensor means to identify acceptable coins.

Description

United States Patent [191 Greene Nov. 18, 1975 1 APPARATUS FOR IDENTIFYING COINS [75] Inventor: Walter John Greene, Sunnyvale,

Calif.

[73] Assignee: Mars, Inc.,McLean,Va.

[22] Filed: Oct. 2, 1974 [21] Appl. No.: 511,433

[30} Foreign Application Priority Data Oct. 3, 1973 United Kingdom 46186/73 [52] US. Cl. 250/557; 194/4 G; 194/97 A; 250/223 R; 250/224; 250/567; 340/1463 AC [51] Int. Cl. G06K 7/14; 007D 5/00; G07F l/O4 [58] Field of Search 194/97 A, 97 R, 4 G, 4 R; 250/222, 223, 556, 55-7, 224, 567, 568;

356/71; 340/1463 AC; 235/61.11 E, 61.11

3,743,820 7/1973 Willits et al. 235/61.11 E

Primary ExaminerEli Lieberman Assistant Examiner-E. R. LaRoche Attorney, Agent, or FirmDavis, Hoxie, Faithfull & I-Iapgood [57] ABSTRACT An apparatus for identifying acceptable coins, including a coin track assembly having a circular coin track loop around which coins can roll, sensor means focused at the center of the circular coin track loop for generating a signal in response to the coin surface pattern as the coin rolls around the circular coin track loop and means for monitoring the signal output from the sensor means to identify acceptable coins.

10 Claims, 3 Drawing Figures US. Patent Nov. 18,1975 Sheet10f2 3,921,003

APPARATUS FOR IDENTIFYING COINS SUMMARY This invention relates to coin discriminators and, more particularly, to a method and apparatus for determining the denomination of coins and for rejecting undesired and counterfeit coins.

Throughout this specification and in the appended claims, the term coin is intended to mean genuine coins, tokens, counterfeit coins, slugs, washers, and any other item which may be used by persons in an attempt to actuate a coin-operated device. An acceptable coin is an authentic coin of the monetary system in which the device is intended to operate and of a denomination which the device is intended selectively to receive for value.

The apparatus and method of the present invention provides a means for examining characteristics of the surface of selected areas of coins in a coin selector. This invention has utility with a coin set of several denominations of varying diameters, as well as with coins of a single diameter. This invention is also suitable for use in conjunction with other coin examining techniques.

IN THE DRAWINGS:

FIG. 1 is a perspective view of a simplified coin track assembly plus a schematic representation of other elements of a coin selector formed in accordance with this invention.

FIG. 2 is a front elevational view of the three coins of a hypothetical coin set which includes a general indication with respect to each coin of the surface area of the coin which would be scanned by one embodiment of this invention.

FIG. 3 is a schematic block diagram of a coin discriminator formed in accordance with this invention.

DETAILED DESCRIPTION A coin discriminator l constructed in accordance with the principles of this invention is shown in FIG. 1. Any of a number of various types of coins (acceptable or otherwise) may be introduced into the coin discriminator through a coin slot 20. The coin 40 falls under the influence of gravity into a coin retarder (not shown). The coin retarder may be any of a variety of mechanical or electro-mechanical arrangements for stopping a coin and then releasing it, e. g., a passageway obstructed by a pin which is mechanically or electromagnetically retracted when a coin comes to rest thereagainst. The coin retarder momentarily brings the coin to rest and then releases it into a coin track assembly indicated generally at 30. All coins, no matter how inserted into coin slot 20, enter coin track assembly 30 under the same initial conditions.

Once in the coin track assembly 30, the edge of the coin 40 bears upon initial track section 31 which is sloped downwardly in a direction away from coin slot and the coin retarder. Coin track assembly may take any of a variety of forms which will hold the coin 40 in a substantially vertical orientation and allow it to roll downward on its edge under the influence of gravity. As shown in FIG. 1, for example, track 30 has a slotted or channel-shaped cross section just wide enough to admit the thickest of the acceptable coins. Further, the upstanding portion 32 of the cross section of track 30 should be high enough to prevent the largest diameter coin, for which the coin discriminator is designed, from falling out of the track; one half of the diameter of such a coin is a suitable height for this purpose.

Advantageously, one form of the initial track section 31 has a large radius of curvature from the start of the initial track section 31 to the beginning of a circular track loop section 34 as shown in FIG. 1. This configuration of initial track section 31 permits a coin to rapidly gather the momentum required to carry it around the circular track loop section 34 and at the same time tends to convert the initial vertical motion of the coin to rolling motion along track 30 with a minimum of coin bouncing. Initially the motion of a coin may be a combination of sliding and rolling. When the coin enters track loop section 34, however, the predominant form of motion will be rolling.

As will be apparent from FIG. 1, a coin 40 rolling down coin track section 31 enters track loop section 34, and if it possesses sufficient momentum rolls up and around circular track loop section 34, and then emerges on a final track section 35. Coins of all acceptable denominations must have sufficient momentum when they enter circular track loop section 34 to maintain firm rolling contact with the coin track of the circular track loop section 34. The physical principles governing motion of this type are discussed, for example, in University Physics by W. F. Sears et al. (Addison-Wesley Publishing Co., Inc., Cambridge, Mass, second Ed. (1955), pp. 107-110). As stated generally therein, an object rolling around a circular track will remain in contact with the circle if its velocity at the top of the circle is at least equal to VER where g is the acceleration due to gravity and R is the radius of the circle.

When coin 40 enters track loop section 34, one or both of its surfaces are advantageously illuminated (to the extent permitted by the presence of circular track loop section 34) by light from a light source or sources (not shown). Considering, for example, only the face of the coin visible in FIG. 1, an optical sensing device 50 is aligned with the axis through the center of the circular track loop section 34. Light reflected from the surface of the coin at a point 52 coincident with the center of the circle defined by the circular track loop section 34 is focused by lens 51 onto the optical sensing device 50. The optical sensing device 50 may be any photosensitive transducer device, e.g., a phototransistor, which produces an electrical output in proportion to the intensity of the light focused on it. It should be appreciated that other types of coin surface characteristic sensors which do not require light may be employed, e.g., high frequency inductors focused at the center of the circular track loop section 34.

In order for a coin to roll around circular track loop section 34, the diameter of the circle measured from the bottom of the channel must be larger than the diameter of the largest acceptable coin. To prevent coins larger than the loop from becoming lodged in track loop section 34, 'such coins may be excluded from the apparatus 10 by appropriate dimensions of the coin slot 20.

It is evident from geometrical considerations that any coin smaller in diameter than one half the diameter of the circular track loop section 34 will reflect no light from the center of the circular track loop section 34 to sensor 50. Accordingly, the ratio of the diameter of the largest acceptable coin to the diameter of the smallest acceptable coin cannot exceed 2 to 1. This ratio can be extended in accordance with the principles of this invention by including two or more progressively smaller loops arranged in series. Large coins can then be identified in the first loop and removed from the coin track while smaller coins pass through the first loop for subsequent identification in a smaller loop. For most coinage, however, a single loop will be sufficient.

FIG. 2 illustrates three hypothetical coins 24011, b, and c each having a distinctive diameter. The diameter d of each of these coins is such that D d /2D where D is the diameter of the circular track loop section 34. Accordingly, any of these coins will pass through track loop section 34 and all are large enough to reflect light from the center of the circular loop 34 to sensor 50. Moreover, it is evident from geometrical considerations that each coin will make between one and two complete revolutions in rolling around track loop section 34, the largest coin making slightly more than one revolution and the smallest coin making almost two revolutions.

Since sensor 50 is focused on the center of the circle defined by circular track loop section 34, sensor 50 scans the surface of these coins at a uniform distance from the edge of the coin as the coin rolls around the circular track loop section 34. Since the focus of the sensor 50 is off the center of any coin and since each coin makes at least one complete revolution in traveling around the circular track loop section 34, sensor 50 scans at least one complete circle on the surface of each coin concentric with the center of the coin. The circles scanned on each of coins 240a, b, and c in FIG. 2 are represented by broken lines 252a, b, and c, respectively. As is evident from FIG. 2, the locus of points scanned on a larger coin 240a defines a circle smaller in diameter than the circle defined by the locus of points scanned on the smaller coin 2400.

The face and denomination of any coin of a denomination accepted by the apparatus can be identified by sampling the output of the sensor 50 during the scanning of a face of a coin searching the samples generated for corresponding key samples associated with each face of all coins of that denomination. If no subset-ofsamples is found to match the key for any acceptable coin, the coin scanned is determined to be unacceptable.

Some extraneous scanning will occur as the coin enters and leaves the circular track loop section 34 (i.e., two lines connecting the edge of the coin with the scanning circle 252a, b, or c will be scanned). This extraneous scanning can be prevented by enabling sensor 50 only while a coin is actually in the circular track loop section 34 or this extraneous scanning information can be ignored in the signal processing, as discussed below. The presence of a coin at any point along the coin track assembly can, of course, be determined, for example, by shining a light through an aperture in the coin track assembly 30 onto a photoelectric device so that occlusion of this light by a coin produces a change in the signal produced by the photoelectric device.

Apparatus for identifying coins from the optical information received by scanning their surface features is shown in FIG. 3. As the coin 340 rolls around the circular track loop section 334 in the manner discussed above in connection with FIG. 1, sensor 350 in conjunction with lens 351 scans a circular region on one face of the coin while sensor 355 in conjunction with lens 356 scans a similar region on the opposite face of the coin. Each of

sensors

350 and 355 therefore produces an output signal progressively representative of the intensity of light reflected by successive points on the scanning circle on the adjacent surfaces of the coin 340. It will be evident that depending on the orientation of coin 340 in track 334, either face of the coin may be presented to either

sensor

350 or 355.

The scanning signals produced by

sensors

350 and 355 are amplified by

amplifiers

360 and 361 and the amplified signals applied to

samplers

362 and 363, respectively. Each

sampler

362 and 363 is responsive to a periodic timing signal produced by clock 366 and produces output signals representative of successive samples of the applied scanning signal. Any of a number of well known signal sampling schemes may be employed. For purposes of illustration, however, each of

samplers

362 and 363 may be assumed to be a simple threshold detector, producing an output signal having one of two levels depending on the level of the applied scanning signal relative to a predetermined threshold level and in response to each timing signal pulse from clock 366.

The pulse rate of the clock 366 is adjusted to compensate for variations in velocity between the coins being examined, so that the same number of bits of information will be sampled for one full circular scan of a coin of a given denomination regardless of its initial velocity. A signal, the duration of which is representative of coin velocity, is obtained by initiating timing when the coin first occludes a sensor from its light source which may be located as indicated by sensor and lamp 71 in FIG. 1 to the time when the coin first reflects light from the lamp (not shown) toward the sensor 350 or from the lamp (not shown) toward the sensor 355. When sensor 70 first receives reflected light, flip-flop 369 is set causing a linear integrator 373, which may be a feedback operational amplifier of conventional design, to begin integration. When sensor 350 first receives light from the lamp (not shown), the flip-flop 369 is reset stopping the period of integration by the integrator 373. A FET follower 374 applies a signalrepresentative of the stored output voltagelevel of the integrator 373 to the input of the clock 366. The clock 366 is advantageously a voltage controlled oscillator in which the output frequency is dependent upon the voltage applied across its input terminals. Adjustment for the range of voltages necessary to provide the desired frequencies is accomplished by known means in the FET follower 374. Such known means may include a voltage divider and a difference circuit.

The digitized output signals thus produced by

samplers

362 and 363 are applied to the input terminals of

multistage shift registers

364 and 365 by way of

switches

371 and 372 which, during this portion of the operation of the apparatus of FIG. 3, are arranged in response to the output signal from a counter 370 to connect the input terminal of each

shift register

364 and 365 to the corresponding

samplers

362 and 363, respectively. Each of the

multistage shift registers

364 and 365 has N stages, each stage capable of storing one scanning signal sample of the type produced by

samplers

362 and 363. In response to each timing signal pulse produced by clock 366, each of the shift registers 364 and 365 shifts the contents of its several stages one stage to the right as viewed in FIG. 3. Simultaneously,

the most recent scanning signal sample produced by each of

samplers

362 and 363 is stored in the initial stage (i.e., the leftmost stage as viewedin FIG. 3) of the corresponding shift register. Each of

shift registers

364 and 365 containsasufficient number of stages (e.g., N) to store all of the scanning signal. samples produced during the scanning of the faces of anyacceptable coin, including the extraneous scanning signal samples resulting from the entry and exit of the coin from the circular coin track loop section 334.

Assuming clock 366 to be arranged to produce N timing pulses during the passage of coin 340 through track loop section-334, N samples of the intensity of the light reflected by each face of the coin, including that produced .upon entry and exit .of the coin from the track loop section 334, will be produced and stored in shift registers-364 and 365 in the manner described above. Counter 370 counts the'timing pulses produced byclock 366. When N pulses have been counted, indicating that N samples of each scanning signal have been produced and stored in the N stages of

shift registers

364 and 365, counter 370 produces an output signal which causes

switches

371 and 372 to change state. When the switches-371 and 372 change state, the last stage of each of the shift registers 364 and 365 is connected to the input terminal-of that shift register forming a closed loop, so that in response to further timing pulses the contents of the last stage of each shift register is continuously shifted back to the input terminal of its

corresponding shift register

364 or 365.

Each

shift register

364 and 365 has a

decoder

367 and 368, respectively; electrically connected thereto to monitor the contents of the shift registers. The

decoders

367 and 368 should possess a bit capacity twice as great as that of the shift registers 364 and 365 to allow identification of a coin whose data sequence may begin or may be interrupted at random, e.g, by a foreign substance on the face of the coin. The required decoder capacity may be more fully appreciated by considering a sequence of data samples where N=8. If the sequence of 8 data samples has additional samplesof spurious data within its sequence, (e.g., from scanning as the coin entered and left the loop), no amount of shifting will produce the proper sequence, i.e., 1, 2, 3, 5, 6, 7,

and 8 in the shift register. Therefore, unless the

decoders

367 and 368 include a bit capacity twice as great as the shift registers 364 and 365, the coin identification becomes unreliable. However, with decoders of the proper bit capacity, i.e., 16 where N=8, the shift registers 364 and 365 may be connected to the

decoders

367 and 368, respectively, so that corresponding data sequences will activate the

decoders

367 and 368 to provide identification of the coin when there is a correspondence between subsets of data samples.

It should be understood that other forms of apparatus may be used to convert the scanned data into useful information. For example, a first shift register feeding a second shift register in series may be employed with a decoder. A switch is used to stop data sampling as the coin begins to leave the loop and to cause the data in the second shift register to be circulated until the data samples attain a correspondence with the decoder. Further, an analog shift register may be employed which sums the current output from the

amplifiers

360 and 361. To decode this information digitally, a read only memory may be employed with the appropriate logic circuitry. Further, when employing an analog shift register a Gray-code analog to digital converter may be advantageously employed. i

V When the contents of the shift registers364 and 365 correspond to the predetermined data pattern for one of the faces of an acceptable denomination coin, within a predetermined tolerance, e.g., 40 percent, an output signal is produced by the

decoders

367 and 368. The output signals from the

decoders

367 and 368 enable appropriate logic circuitrytnot shown) when predetermined subsets of data samples in the shift registers 364 and 365 correspond with those in the

decoders

367 and 368. For example, in a coin selector in which current United States coinage in the 5-cent, l0-cent and 25- cent denominations is to be accepted, the outputs from the decoders367 and 368 and appropriate logic circuitry (not shown) have been designated in FIG. 3 as follows: 5H, 5T, lOI-I, 10T, 25H and 25T, where the numerals designate the denomination and H and T (heads and tails) designate the two faces of the coins.

The outputs from the

decoders

367 and 368 andappropriate logic circuitry (not shown) are connected so that the H output for each denomination from decoder 367 is connected to the same AND gate as the T output for the same denomination from decoder 368, and vice versa. As a result, when a coin is determined to have the characteristics of a genuine 5-cent piece on both faces, either AND

gate

380 or 381 will be activated, depending on the orientation of the coin with respect to

sensors

350 and 355. The output from the AND gates 380 and'381 is connected to an EXCLUSIVE OR gate 386 and the output from the EXCLUSIVE ORgate 386 to a flip-flop 391. The output from the EXCLUSIVE OR gate will set flip-flot 391. Similarly, in the case of a 10-cent piece, AND

gates

382 or 383 will be activated'and flip-flop 392 will be set via EXCLUSIVE OR gate 387', andin the case of a 25cent piece, AND gates 384 or 385 will be activated and flip-flop 393 will be set via EXCLUSIVE OR gate 393. The flip-flops 391, 392 and 388, as well as the shift registers 364 and 365 are reset by a resetting means indicated at 375 after the coin has exited from the final coin track 35.

The transition in the signal output which occurs when the coin leaves the track 334 and sensor 350 no longer receives light from lamp (not shown) causes a pulse at the output of a capacitor (not shown) which is applied to one input of each of the AND

gates

402, 404 and 406. The other input of each of these AND gates is the output of the flip-flops 391, 382 and 393, respectively. When the transition pulse is applied to the AND

gates

402, 404 and 406, the state of the flip-flops 391, 392 and 393 is interrogated, and, in the event that one of the flip-flops is set, the associated AND gate produces an output signal, indicative of the acceptability of a coin of the associated denomination, which passes through OR gate 408 to activate solenoid 396 causing the coin to be directed to an acceptable coin container (not shown). The output signal from the AND

gates

402, 404 and 406 also passes directly to an accumulator 398 where the acceptance of the coin of the particular denomination is recorded.

In addition to the coin track loop assembly 30, FIG. 1 also indicates, schematically, two inductors and 81, one or both of which may be used in accordance with my invention to provide more accurate discriminations against counterfeit coins, slugs and the like. A high degree of discrimination is provided by use of inductive sensing of coin material characteristics at two widely separated frequencies as disclosed in UK specifications numbers 16538/71 and 83 85/72. Another variant of my invention employs a coin impeller of the type disclosed in UK specification number 43014/70 and US. patent application Ser. No. 120,652 of Mar. 3, 1971 to move the coin along the coin track rather than employing gravity; in which case the velocity of acceptable coins would be predictable, therefore the clock 366 could have a fixed output frequency and sensor 70 and its associated circuitry could be eliminated.

What is claimed is:

1. An apparatus for identifying acceptable coins, comprising a coin track assembly including a circular coin track loop around which coins can roll, sensor means focused at the center of the circular coin track loop for generating a signal in response to the coin surface pattern as a coin rolls around the circular coin track loop, and means for monitoring the signal output from the sensor means to identify acceptable coins.

2. The apparatus claimed in claim 1 wherein said coin track assembly includes an initial coin track section coupled to said circular coin track loop, said initial coin track section having a large radius of curvature to permit a coin to gather the momentum required to carry it around said circular coin track loop.

3. The apparatus claimed in claim 1 wherein said sensor means includes two optical sensing devices positioned on opposite sides of said circular coin track loop and focused at the center of said circular coin track loop.

4. The apparatus claimed in claim 1 wherein said sensor means produces an analog output, said monitoring means includes means for converting the analog output from said sensor means into digital information, means for sequentially storing said digital information, and means for decoding the sequentially stored digital information by comparison with predetermined data subsets representative of an acceptable coin surface pattern.

5. The apparatus claimed in claim 4 including coin velocity determining means for controlling the number of digital conversions made by said converting means.

6. An apparatus for identifying acceptable coins, comprising:

a coin track assembly including a circular coin track loop around which coins can roll, the circular track loop having a diameter greater than the diameter of the coins to be identified and less than two times as great as the diameter of the coins to be identified;

sensor means focused at the center of the circular coin track loop for generating a signal in response to the coin surface pattern as a coin rolls around the circular coin track loop; and

means for monitoring the signal output from the sensor means to identify acceptable coins.

7. The apparatus claimed in claim 6 wherein said coin track assembly includes an initial coin track section coupled to said circular coin track loop, said initial coin track section having a large radius of curvature to permit a coin to gather the momentum required to carry it around said circular coin track loop.

8. The apparatus claimed in claim 6 wherein said sensor means includes two optical sensing devices positioned on opposite sides of said circular coin track loop and focused at the center of said circular coin track loop.

9. The apparatus claimed in claim 6 wherein said sensor means produces an analog output, said monitoring means includes means for converting the analog output from said sensor means into digital information, means for sequentially storing said digital information, and means for decoding the sequentially stored digital information by comparison with predetermined data subsets representative of an acceptable coin surface pattern.

10. The apparatus claimed in claim 9 including coin velocity determining means for controlling the number of digital conversions made by said con-

Claims

6. An apparatus for identifying acceptable coins, comprising: a coin track assembly including a circular coin track loop around which coins can roll, the circular track loop having a diameter greater than the diameter of the coins to be identified and less than two times as great as the diameter of the coins to be identified; sensor means focused at the center of the circular coin track loop for generating a signal in response to the coin surface pattern as a coin rolls around the circular coin track loop; and means for monitoring the signal output from the sensor means to identify acceptable coins.

10. The apparatus claimed in claim 9 including coin velocity determining means for controlling the number of digital conversions made by said converting means.